Pressure strainer device

ABSTRACT

Pressure strainer device for cellulose, paper or equivalent pulp suspension comprising at least one straining cylinder, through which the acceptable pulp is strained and in connection with which there is provided at least one vane revolving about its axis and moving at a small distance from it and which vane cleans the face of the straining cylinder facing the pulp to be strained and which vane has for the purpose of collecting the rejected pulp a cavity extending from one end to the other and opening through a slot towards the straining cylinder and communicating at one end with the reject space. The reject space is separated from the entry space of the pulp to be strained by a secondary straining cylinder, through which the acceptable pulp still travelling along with the rejected pulp is strained and in connection with which there is provided at least one secondary vane revolving about its axis and moving at a small distance from it, which secondary vane cleans the face of the secondary straining cylinder facing the reject space.

Salminen 1 PRESSURE STRAINER DEVICE Rauno Salminen, Valkeakoski, Finland [73] Assignee: Yhtyneet Paperitehtaat 0y Jylhavaara, Valkeakoski, Finland 22 Filed: Aug. 30, 1972 21 Appl. No.: 284,867

[75] Inventor:

[30] Foreign Application Priority Data June 21, 1972 Finland 1773/72 [52] US. Cl 209/240, 209/273, 207/306, 209/379, 210/415 [51] Int. Cl. B07b 1/00, 1307b 1/50 [58] Field of Search 209/273, 305, 270, 306, 209/379, 240; 210/415 [56] References Cited UNlTED STATES PATENTS 1,134,304 4/1915 Westbye 209/273 1,537,691 5/1925 Prievy 209/273 3,168,467 2/1965 Dreyer 210/415 X 3,232,436 2/1966 Nilsson 210/415 X 3,394,809 7/1968 Monte 209/273 3,399,772 9/1968 Salomon 209/273 3,726,401 4/1973 Bolton 209/306 3,759,392 9/1973 Syrsanen 210/415 1 Febrll, 1975 FOREIGN PATENTS OR APPLICATIONS 660,707 4/1963 Canada 209/273 Primary Examiner-Robert Halper [57] ABSTRACT Pressure strainer device for cellulose, paper or equivalent pulp suspension comprising at least one straining cylinder, through which the acceptable pulp is strained and in connection with which there is provided at least one vane revolving about its axis and moving at a small distance from it and which vane cleans the face of the straining cylinder facing the pulp to be strained and which vane has for the purpose of collecting the rejected pulp a cavity extending from one end to the other and opening through a slot towards the straining cylinder and communicating at one end with the reject space. The reject space is separated from the entry space of the pulp to be strained by a secondary straining cylinder, through which the acceptable pulp still travelling along with the rejected pulp is strained and in connection with which there is provided at least one secondary vane revolving about its axis and moving at a small distance from it, which secondary vane cleans the face of the secondary straining cylinder facing the reject space.

4 Claims, 2 Drawing Figures PRESSURE STRAINER DEVICE The pulp sorting process is based on a construction in which the holes in the straining cylinder pass acceptable fibres. However, the size of the holes is always larger than the size of the acceptable fibres, because sufficiently small holes are associated with difficulties in manufacture and because the capacity of a straining cylinder with sufficiently small holes would be substantially reduced. Therefore, the accepted pulp always also contains particles to be rejected, fibre bundles, sticks, etc. On the other hand among the rejected pulp there are also always found acceptable fibres, and their amount increases with decreasing size of the holes in the straining cylinder.

Recovery of acceptable fibres from the rejected pulp has heretofore taken place by passing rejected pulp through a second pressure straining device. The acceptable pulp obtained herefrom is once more introduced into the first-mentioned pressure straining device.

An object of the present invention is to improve the first-mentioned pressure straining device so that no second pressure straining device is needed at all, whereby considerable savings are achieved in initial costs, operating costs and maintenance costs. A pressure straining device according to the invention is characterized in that a reject space is separated from the entry space ofthe pulp to be strained by means of a secondary straining cylinder, through which acceptable pulp travelling along with the rejected pulp is strained and in connection with which there is provided at least one secondary vane revolving about its axis and moving at a small distance from it, this vane cleaning the face.

of the secondary straining cylinder facing the reject space. lt is thus seen that in a pressure straining device according to the invention the rejected pulp is subjected to another straining operation. The accepted pulp obtained at this secondary straining goes immediately back into the entry space of the pulp to be strained, while the final rejected goods may be discharged e.g. to the sewer.

According to a structurally simple embodiment of the invention, the vane and secondary vane are integrally attached to one and the same rotor.

The invention is described hereafter in regard to an embodiment thereof and with reference to the attached drawing, wherein:

FIG. 1 shows a pressure straining device in longitudinal section taken along line ll in FIG. 2; and

FIG. 2 is a section taken along line ll'lI inFlG. 1.

Pulp suspension is supplied under pressure through the pipe 1 into an entry space or inlet chamber 2 for the pulp to be strained, this space being confined on the outside by a jacket 3 and on the inside by a straining cylinder 4. Associated with the straining cylinder 4 are two vanes 5 revolving about its axis and moving at a small distance from it and which clean the outer surface of the straining cylinder. The vanes 5 are attached to the ends of a transversal arm 6 rotating along with the shaft 7. The lower ends of the vanes 5 are connected by a continuous bracing ring 8, which prevents the downward travel of the pulp to be strained in the entry space.

.The accepted pulp flows through the straining cylinder 4 from the entry space 2 into the annular space 9 and thence through the exit pipe 10 for further treatment. Simultaneously with the passage of the accepted 2 pulp through thestraining cylinder 4, a pulp layer enriched with rejected particles forms on its outer surface. The vanes 5 remove this layer as it is formed. The vanes 5 have a cavity 11 extending longitudinally therealong and opening through a slot 12 towards the straining cylinder 4. At the .lower end the cavity 11 opens through the bracing ring 8 into a reject space or collection chamber 13. At its upper end the cavity 11 is closed. The rejected pulp is detached from the outer surface of the straining cylinder 4 by the suction produced by the vane 5 and passes through the slot 12 in I the vane, under the effect of dynamic pressure and centrifugal force, into the cavity 11 and then into the reject space 13.

According to the invention, the reject space 13 is externally bounded by a secondary straining cylinder 14 which communicates with the entry space 2 so that acceptable pulp still accompanying the rejected pulp is strained by cylinder 14 and passed into entry space 2. In order to achieve this, two downwardly projecting secondary vanes 15 are attached to the bracing ring 8, which move at a small distance from the inner surface of the secondary straining cylinder 14. The lower ends of the secondary vanes 15 are connected by a continuous closing ring 16, which prevents the downward flow of the rejected pulp. The accepted pulp flows through the secondary straining cylinder 14 from the reject space 13 back into the entry space 2, where it rises upward and is once more exposed to the effect of the vanes-5. Simultaneously with the passage of acceptable pulp through the secondary straining cylinder 14, on the inner surface of this cylinder a pulp layer enriched with reject particles is formed. The secondary vanes remove this layer as it is formed. The secondary vanes have a cavity 17 extending longitudinally thereof and opening through a slot 18 towards the secondary straining cylinder. On the other hand the cavity 17 opens through the closing ring 16 into the secondary reject space or collection chamber 19 and further into the discharge pipe 20.

It is obvious to one skilled in the art that different modifications of the invention may vary within the scope of the claims presented below. For instance, the number of straining cylinders 4 may be two .or more,

concentricallyplaced and at least one vane 5 being provided in association with each. Thesame applies to the secondary straining cylinders 14 and secondary vanes 15. The number of vanes in association with one straining cylinder is not limited in any way. As shown in the drawing, the reject spaces 13 and 19 are located in the I lower part of the pressure straining device, but they may be equally well provided in the upper part of the straining device.

As seen in the drawing, the vane 5 moves onthe outside of the straining cylinder 4 and the secondary vane 15 moves on the inside of the secondary straining cylinder 14. However, their locations may be reversed if the pulp to be strained is introduced into the central part of the pressure straining device.

What is claimed is:

1. A pressure straining device for a pulp suspension comprising an inlet chamber for pulp to be strained, at least one straining cylinder bounding said inlet chamber and through which acceptable pulp is strained, at least one rotatable vane movable in said inlet chamber proximate the surface of said straining cylinder, said vane having a cavity extending therein, one end of which is closed, said cavity extending along the vane longitudinally and saidvane having a slot leading into said cavity and facing said surface of the straining cylinder to admit unstrained pulp collected on said surface into said cavity, a collection chamber having means for isolating itself from said inlet chamber, said cavity of said vane communicating at the other end thereof with said collection chamber for introducing said unstrained pulp thereinto, a secondary straining cylinder concentric with said first screening cylinder, extending outwardly and below said first straining cylinder and forming a separating screen between said collection chamber and said inlet chamber to strain said pulp received from the cavity of said vane, acceptable pulp passing thru said secondary straining cylinder and moving upwardly tosaid inlet chamber for admixture with the pulp coming thereinto; and at least one secondary rotatable vane movable along the surface of said secondary straining cylinder to clean said surface of the secondary straining cylinder.

2. A pressure straining device according to claim 1 comprising a common rotor to which the first and secondary vane are integrally attached.

3. A pressure straining device according to. claim 1 wherein the surface of the first said straining cylinder on which the vane moves is the outer surface thereof whereas the surface of the secondary straining cylinder on which the secondary vane moves is the inner surface thereof.

4. A pressure straining device according to claim 1 wherein said secondary vane has a cavity therein one end of which is closed, said cavity, extending along the vane longitudinally, a slot leading into said cavity and facing said secondary straining cylinder to admit collected pulp thereon into said cavity, said cavity in said secondary vane leading into a secondary collection chamber. 

1. A pressure straining device for a pulp suspension comprising an inlet chamber for pulp to be strained, at least one straining cylinder bounding said inlet chamber and through which acceptable pulp is strained, at least one rotatable vane movable in said inlet chamber proximate the surface of said straining cylinder, said vane having a cavity extending therein, one end of which is closed, said cavity extending along the vane longitudinally and said vane having a slot leading into said cavity and facing said surface of the straining cylinder to admit unstrained pulp collected on said surface into said cavity, a collection chamber having means for isolating itself from said inlet chamber, said cavity of said vane communicating at the other end thereof with said collection chamber for introducing said unstrained pulp thereinto, a secondary straining cylinder concentric with said first screening cylinder, extending outwardly and below said first straining cylinder and forming a separating screen between said collection chamber and said inlet chamber to strain said pulp received from the cavity of said vane, acceptable pulp passing thru said secondary straining cylinder and moving upwardly to said inlet chamber for admixture with the pulp coming thereinto, and at least one secondary rotatable vane movable along the surface of said secondary straining cylinder to clean said surface of the secondary straining cylinder.
 2. A pressure straining device according to claim 1 comprising a common rotor to which the first and secondary vane are integrally attached.
 3. A pressure straining device according to claim 1 wherein the surface of the first said straining cylinder on which the vane moves is the outer surface thereof whereas the surface of the secondary straining cylinder on which the secondary vane moves is the inner surface thereof.
 4. A pressure straining device according to claim 1 wherein said secondary vane has a cavity therein one end of which is closed, said cavity, extending along the vane longitudinally, a slot leading into said cavity and facing said secondary straining cylinder to admit collected pulp thereon into said cavity, said cavity in said secondary vane leading into a secondary collection chamber. 